Circulating Cardiac miRNAs Distinguish Ischemic vs. Non‐Ischemic Myocardial Injury in Swine

Abstract

ObjectiveWe have recently demonstrated that brief ischemia‐induced myocardial stunning and mechanical stretch from a transient elevation in left ventricular (LV) preload each elicit myocyte apoptosis and a significant rise in serum cardiac troponin I (cTnI) concentrations in swine, despite the absence of pathologic evidence of infarction or necrosis. These results challenge the notion that elevated cTnI is a specific indicator of myocardial infarction (MI) and support exploration of new biomarkers that may improve diagnostic accuracy following myocardial injury. The present study was designed to determine whether cardiac miRNAs exhibit distinct patterns of release in 3 different porcine models of myocardial injury: prolonged ischemia‐induced MI, brief ischemia‐induced myocardial stunning, and elevated preload‐induced myocardial stretch.MethodsClosed‐chest propofol‐anesthetized swine were subjected to one of three myocardial injury protocols: 120 min ischemia (“MI”; n=10), 10 min ischemia (“stunning”; n=5), or 60 min elevated preload (“stretch”; n=14). Ischemia was produced via balloon occlusion of the distal LAD, while intravenous phenylephrine (300 μg/min) was used to transiently raise LV end‐diastolic pressure without affecting coronary blood flow. Echocardiography was performed in all protocols to evaluate LV function. Circulating concentrations of miR‐1, miR‐133a, miR‐133b, and miR‐499 in peripheral venous blood were measured by quantitative RT‐PCR at baseline and 24 hours after myocardial injury. PCR‐derived quantification cycle (Cq) values were normalized to a synthetic control (cel‐miR‐39) that was spiked in during RNA extraction and all data were expressed as a fold‐change vs. baseline. Serum cTnI values were assessed by a porcine‐specific ELISA.ResultsAnimals subjected to brief ischemia‐induced stunning or preload‐induced stretch were distinguished from animals with MI by the presence of reversible LV dysfunction without pathologic evidence of infarction or necrosis. Nevertheless, serum cTnI concentrations rose significantly after myocardial injury in each group (MI: 14368±2678 ng/L; stunning: 1021±574 ng/L; stretch: 1520±616 ng/L; all p<0.05 vs. baseline). miR‐499 exhibited a similar pattern of release, increasing after MI (531‐fold change vs. baseline, p<0.01), stunning (986‐fold change vs. baseline, p<0.01), and stretch (29‐fold change vs. baseline, p<0.01). Brief ischemia‐induced stunning also elicited a rise in circulating concentrations of miR‐1 (8‐fold change vs. baseline, p=0.07), miR‐133a (10‐fold change vs. baseline, p=0.02), and miR‐133b (6‐fold change vs. baseline, p=0.03). In contrast, concentrations of these miRs remained unchanged in swine subjected to stretch‐induced injury (miR‐1: p=0.62 vs. baseline; miR‐133a: p=0.43 vs. baseline; miR‐133b: p=0.87 vs. baseline).ConclusionCardiac miRNAs differ in their pattern of release into the bloodstream following various types of myocardial injury. Similar to cTnI, circulating concentrations of miR‐499 rise significantly after MI, stunning, and stretch. In contrast, plasma levels of miR‐1, miR‐133a, and miR‐133b increase after ischemia‐induced injury, regardless of duration, but do not change after stretch‐induced injury when ischemia is absent. These findings have implications for the use of circulating miRNAs as clinical biomarkers and suggest that they may be useful in differentiating ischemic vs. non‐ischemic myocardial injury.Support or Funding InformationThe National Heart Lung and Blood Institute (HL‐055324 and HL‐061610), the American Heart Association (17SDG33660200), the National Center for Advancing Translational Sciences (UL1TR001412), the Department of Veterans Affairs (1IO1BX002659), and the Albert and Elizabeth Rekate Fund in Cardiovascular Medicine.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.